There have been many varieties of polyethylene polymers polymerized over the years, including those made using high pressure free radical chemistry (LDPE), more traditional linear low density polyethylene (LLDPE) typically made using Ziegler-Natta catalysts or metallocene or constrained geometry catalysts. Some linear polyethylenes, but also some substantially linear polyethylenes, contain a slight amount of long chain branching. While these polymers have varying positives and negatives—depending on application or end-use—more control over the polymer structure is still desired.
We have now found that post-metallocene catalysts can efficiently polymerize ethylene into polymers and polymer compositions having controlled comonomer distribution profiles, while also controlling unsaturation levels in the polymer.